1. Field of the Invention
This invention pertains to devices for disorienting adversaries. More particularly, light- and sound-producing apparatus is provided in a device that may be hurled or projected toward a person to be temporarily disoriented.
2. Description of Related Art
Currently, military, law-enforcement, and other agencies rely on pyrotechnic stun grenades as a non-lethal means of visually distracting, disorienting, or temporarily disabling personnel. The current generation of stun grenades have modest proven effectiveness, last only a short time, can injure the user or innocent bystanders and cannot be used where there is a danger of starting a fire or in areas where explosive gases are present (e.g. ship holds, aboard aircraft, methamphetamine laboratories). Accordingly, there is a need for a non-pyrotechnic replacement for the existing stun grenades that provides the capability of disorienting adversaries. There is also a need for a safe, reuseable, non-pyrotechnic projectile for training law enforcement or military personnel for certain scenarios where disorienting an adversary or adversaries is advantageous. In this case, for training, the non-pyrotechnic projectile would substitute for the pyrotechnic version. In this case, for training, the non-pyrotechnic projectile would substitute for the pyrotechnic version. In addition, there is a need for a safe, reuseable non-pyrotechnic projectile for disorienting opposing players (simulated adversaries), or for simulating grenades or other explosive devices in the game of “paintball” or other similar simulated warfare games.
At present, commercially available optical less-than-lethal systems can be divided into two categories: stun or flash-bang grenades, and laser dazzlers. Each of these systems has certain advantages and limitations. Flash-bang devices, such as the M84 Stun Grenade, manufactured and sold by Goodrich Universal Propulsion Company (UPCO), combine bright light (1 million candela) and painful sound levels (170 dB) to confuse, distract and disorient personnel. However, detonation of stun grenades in the presence of natural gas, gasoline, solvents, or other flammable fumes or materials may result in serious secondary explosions or fire. In addition, injury to personnel could result if the grenade activates prior to being deployed or if it lands too close to an adversary or bystander.
Laser dazzlers use red or green diode lasers operating in a pulsed or continuous format to temporarily blind or obscure the vision of adversaries. However, concerns over eye safety of these devices are limiting their use. A similar device called the Veiling Glare Laser is under development that uses 365 nm laser light to cause the eyes' lens to fluoresce, causing the retina to be flooded with light that interferes with normal image formation. Laser dazzler devices are inherently very directional, thereby limiting their utility for crowd dispersal or for instances where there is more than one adversary.
In a discussion of human response to visible optical energy, it is important to distinguish between the physical description of the incident electromagnetic wave and the visual perception of that incident wave by the human eye and brain. Light is defined as the visual sensation of radiant power. Radiant power (or radiant flux) is a physical term and is equal to the amount of electromagnetic wave energy per unit time. Photometry describes the visual perception of light from a human observer standpoint and can be described as the aspect of radiant power that evokes a visual sensation as a result of stimulation of the human retina. The wavelength range that normal humans can perceive is from approximately 400 nm to 700 nm. For an equal radiant power at every wavelength across the visual spectrum, the normal human observer will perceive a wavelength-dependent brightness that is a function of the spectral responsivity (sensitivity as a function of wavelength) of the rods and cones that comprise the retina. The standard response of normal daylight-adapted humans (photopic vision) is centered at approximately 555 nm and decreases uniformly for both shorter and longer wavelengths. The responsivity of the human eye at 480 nm (blue-green light) is only about 1/10th that of 555 nm (yellowish green) light. Therefore, when exposed to equal irradiances (W/cm2) of 480 nm and 555 nm light, a normal daylight-adapted human will perceive the 555 nm light to be ten times as bright. It is worthwhile to also note that the responsivity of the standard human dark-adapted eye (scotopic vision) is blue-shifted with respect to photopic vision, and is centered around 510 nm (green). Therefore, light with wavelengths from 510 nm to 555 nm provide the highest human visual response per unit of radiometric power. This is an important ingredient for the development of a high-intensity light source designed to startle, disorient, or temporarily incapacitate in either a day or night situation.
Repetitively flashing lights have been shown to cause seizures and disorientation in both epileptics and normal humans. Because of this, many countries have laws governing the use of flashing lights in public places. Effects such as nausea, vomiting and seizures have been directly linked to the excessive use of flashing lights at repetition frequencies from 3-15 Hz. Military programs dating back to World War I have investigated the use of high-power strobe lights as a source to disorient, and even create seizures in enemy forces.
It is well known that bright lights, particularly those with wavelengths near the peak of the human retinal responsivity can cause glare, flashblindness and afterimages. These effects can cause disorientation of humans because of loss or degradation in their visual function. The possible adverse effects on vision as a result of exposure to very bright light sources can vary from the relatively minor glare, to flashblindness, and finally to debilitating (and permanent) retinal lesions as the radiant exposure (or irradiance) increases. It is worthwhile to note that looking directly in to the sun for more than one second can cause permanent damage to the human retina. The particular negative effect on vision will be both a function of the light source characteristics (e.g. wavelength, power or energy, pulse-width, repetition frequency, etc.), the state of adaptation of the observer (photopic or scotopic vision), and propagation effects (e.g. atmospheric scattering, absorption, and reflection from other objects).
Unlike coherent radiation from a laser that focuses to a small spot on the retina and thus produces a high peak radiant power density on the retina, the extended source of an incoherent light generates a broadened image on the human retina and thus a larger spot size with a correspondingly lower peak radiant power density. It is well known that incoherent sources of light are thus much safer than a coherent light source of the same total power. In addition, the larger retinal image of an incoherent source increases the vulnerability of the observer to transient effects such as glare or flashblindness, and will obscure a larger part of the observer's field of vision. Definitions for the transient visual effects of glare, flashblindness, and afterimages are given below:
Glare: a reduction or total loss of visibility, such as that produced by the sun, searchlights, or headlights. These visual effects last only as long as the light is actually present affecting the individual's field of vision. Exposure to continuous wave or rapidly pulsed visible light can produce glare and can interfere with vision even at radiant powers well below those that produce permanent eye damage.
Flashblindness: inability to detect or resolve a visual target following exposure to a bright light, similar to that produced by flashbulbs. It can occur at irradiance levels well below those that cause eye damage. Visible light can produce a lingering yet temporary visual loss associated with spatially localized after-effects. This impairment is transitory, depending upon the light source exposure level and time, the visual task, the ambient lighting, the observer's level of adaptation, and the brightness of the visual target.
Afterimage: perception of light, dark, or colored spots after exposure to a bright light. Small afterimages, through which one can see, may persist for several minutes or even hours.
The irradiance or radiant exposure at the retina for a light source is also a function of pupil size since the area of the pupil determines how much light enters the eye. The average pupil is 2-3 mm in diameter for normal daylight viewing and will dilate to around 7 mm in a dark environment. Generally speaking, the dark adapted eye will allow 10 times more light into the eye during exposure than the light adapted eye. This makes personnel at night, already confronted with low contrast targets, the most susceptible to the adverse effects of overexposure to light.
To protect individuals from the hazards of laser and broadband light exposure, the American National Standards Institute and other international safety organizations use maximum permissible exposure (MPE), which is defined as that level of light radiation to which a person may be exposed without suffering any adverse biological effects. However, the MPE does not take into account transient effects such as glare and flashblindness. The safety standards and MPE were established based on experimentally determined threshold levels for optically-induced damage to biological tissues. MPE limits are expressed in terms of irradiance (W/cm2) or radiant exposure (J/cm2) and are a function of wavelength and exposure duration. It is important in the development of a less-than-lethal technology to stay well below irradiance damage thresholds, taking into consideration the worst-case observer-source geometry and the largest pupil diameter and stare time.
Adams (U.S. Pat. No. 5,222,798) describes a self contained, self powered, bright light source in a strong case having a transparent dome that is thrown or fired into position. Once activated, the light source may not be readily deactivated and will shine sufficiently bright so as to be temporarily blinding to the direct view of any human who is close enough to the light source to touch it. Minovitch (U.S. Pat. No. 5,234,894) describes a flashlight type device with energy storage capacitors and a flashtube that can create a high intensity light to temporarily blind an assailant at a distance. The flash is focused by a reflector to form a concentrated beamed light flash which is aimed at an assailant's head. Ripingill (U.S. Pat. No. 6,065,404) describes a simulated grenade that is meant for simulating a pyrotechnic fragmentation grenade and is not intended to visually disable personnel in the vicinity of its blast. A plurality of transducers such as infrared LED's, acoustic transducers or RF transducers are located in the core for emitting signals detectable by a plurality of sensors worn by a player within a predetermined proximity of the simulated grenade.
Tocci (U.S. Pat. No. 6,190,022) describes a self contained non-lethal security device for providing an optimally effective and eye-safe beam for use as a high brightness visual countermeasure. The device has one or more wavelengths of laser or LED light in a continuous or flicker mode in order to provide a glare or flashblinding visual effect. The device is apparently not intended to be used as a projectile, and has no provision for sound output nor extending the effective source size of the light. In addition, Tocci teaches the use of LED devices that are encapsulated in plastic and soldered to a printed circuit board, just as a normal electronic component might be. The size of the commercial LED packaging limits the density of LEDs that can be put on a single circuit board. In addition, the commercial LED package has poor thermal conductivity, limiting LED radiant output. The limited density and poor thermal characteristics of the Tocci design limit the realizable radiant output to values less than those required to produce any visual effect in an adversary.
Brown (U.S. Pat. No. 6,799,868) describes a laser flashlight that employs an emitter disposed within a housing for emitting a coherent light beam having a gaussian spatial profile along an optical axis toward the exit face of the housing. An optical system disposed within the housing intermediate to the emitter and the exit face of the housing includes a laser element pumped by the emitter, a frequency/wavelength converter, and a resonator, to form the coherent light into a laser beam. A beam expander receives the laser beam, disperses the laser beam, and transmits the dispersed laser beam from the light emitting end of the housing into the ambient environment. The device does not support the visual impairment of adversaries over a broad range of angles, must be aimed and has no capability of being thrown or projected.
The limitations of the currently available less-than-lethal optical devices demonstrate that new systems are needed for use in situations where the laser dazzler and stun grenade are inappropriate, ineffective, or lead to potentially hazardous situations for either the deploying person or to the adversaries. What is needed is a non-lethal optical device using a non-coherent source of light, such as arrays of light-emitting diodes (LEDs) or a high-pressure discharge lamp, that can create a disorienting or vision-obscuring glare in adversaries without the above-mentioned issues of eye safety or ignition of flammable materials. Such devices are also needed for recreational purposes to be used in simulated military or police activities.